Reinforced ceramic matrix composite articles (CMCs) are well suited for structural applications because of their toughness, thermal resistance, high temperature strength and chemical stability. To make a CMC article, fiber is initially shaped to create a preform, the preform is then rigidized with a ceramic phase(s) and the porosity within the preform is filled with a ceramic slurry bonded by a molten alloy infiltrant.
For example, silicon carbide (SiC) matrix composites have been made by infiltrating a silicon carbide slurry into a porous fiber preform to form a green composite article. A molten alloy infiltrant material including silicon (Si) may then be introduced into the green composite article using capillary forces to densify the structure to less than about 5% porosity and form a CMC article.
To most effectively infiltrate the pores of the fiber preform with slurry, the slurry should have a relatively low viscosity. However, the SiC particles in the slurry should be maintained within the pores of the preform to ensure optimum densification of the article during this step as well as to ensure that the molten alloy infiltrant is efficiently wicked into the slurry infiltrated green composite article. A small amount of slurry can be lost from the preform pores after slurry infiltration, and this effect becomes particularly acute with lower slurry viscosities.